Polyaspartic acid has been formed by a number of methods. U.S. Pat. No. 5,116,513 to Koskan et at. teaches the formation of polyaspartic acid by the thermal polymerization of aspartic acid. The polymerization produces a polysuccinimide, which is then base hydrolyzed to polyaspartic acid.
U.S. Pat. No. 4,839,461 to Boehmke teaches the production of polyaspartic acid by reacting maleic acid and ammonia in a molar ratio of 1:1 to 1.5 at the relatively low temperatures of 120.degree.-150.degree. C.
Mosig, "Kinetic and Thermal Characterization of the Hydrolysis of Polysuccinimide", Diplomarbeit Thesis, Clemson University, Clemson, S.C., April 1992, demonstrated that the rate of base hydrolysis of polysuccinimide to polyaspartate is dependent on hydroxide concentration and temperature, and that the temperature has a pronounced effect on the rate.